<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      * {
        margin: 0;
      }
      .flex {
        display: flex;
        flex-direction: column;
        min-height: 100vh;
      }
      .header {
        height: 100px;
        background-color: #fac;
      }
      .footer {
        height: 199px;
        background-color: #cfa;
      }
      .main {
        background-color: #acf;
        flex-grow: 1;
      }
    </style>
  </head>
  <body>
    <div class="flex">
      <div class="header">HEADER</div>
      <div class="main">MAIN</div>
      <div class="footer">FOOTER</div>
    </div>
  </body>
</html>

